The purpose of this research is to delineate barriers, pathways, and transport mechanisms within the normal and altered cochlea using qualitative and quantitative electron microscopic investigative techniques. Anatomical barriers and pathways within the cochlea will be altered by histamine and diuretics and studied by visual tracers such as horseradish peroxidase and glycogen. Our objective is to delineate compartments of the membranous labyrinth (endolymphatic, perilymphatic, vascular) and the types, amount, and pathways of exchange between these compartments. Our ultimate goal is to understand the function of the membranous labyrinth, both under normal conditions and in abnormal states such as endolymphatic hydrops and sudden deafness.